C11Edge vs TOA 130 2.0

[Rodd]

This post id for those of you who insist the C11edge out perfroms the TOA 130.  Let's be clear--the C11Edge does outperfrom the TOA 130 in good seeing.  However, I rarely get good seeing.  Last night I lost 25% of my subs due to dewing issues with the C11Edge, and if breezy, I lose many more.  My point is on paper the C11Edge may outperform the TOA 130, but in the field, at my location, that represents maybe 10% of the time.  Maybe more--determining a number is impossible.  I'll just say it is less than 50% of the time.  And I think far less.

In this case I am comparing Ha stacks of the same target, registered to the C11Edge data.  The only processing that was perfromed was crop edges, DBE, and a histogram stretch to just below the noise threshold (or there abouts, there is still some noise as I wanted the images to be bright enough for this post).  the histpgram stretches were the same.  The TOA has a wider curve, which is apparent from the brightness, but the peaks of the histograms were in teh same location. The C11Edge image has 60 subs and the TOA image has 69 subs.  Most subs were 300 sec, but 12 subs for the C11EDge were 500 sec.  And still, the TOA image to my eye is better.  It has a lower FWHM (2.1 vs 2.4).  It is strange that teh C11 image is 9.4 mb while the TOA imnage is only 4.2.  Probably becuase the piel scale for the C11 image is .4" while the native piel scale of the TOA image was 1.12'.  I thought that when  registered, the pixel scales would become the same.  Apparently that is not the case.  In any event, if this is the difference between the two scopes most of the time, I resubmitt the query, why use the C11Edge?  The TOA can be cropped to the same size/scale.  The caveat is that I do not set up each night.  I switch scopes about once per year--sometimes every 2 years.  So using the C11 during good seeing and the TOA in less tha  goos seeing is not an option.

C11Edge

TOA 130

[tomato]

I agree the TOA 130 is the better image. I was convinced by @ollypenrice’s article regarding using a 6” 1m FL refractor vs 2m+ FL reflector for galaxy imaging and do not regret going with Esprit 150s for this purpose. I do change my set up at least once per year and it is an added bonus that the refractor is much more robust to accommodate this.

[ollypenrice]

2 hours ago, tomato said:

I agree the TOA 130 is the better image. I was convinced by @ollypenrice’s article regarding using a 6” 1m FL refractor vs 2m+ FL reflector for galaxy imaging and do not regret going with Esprit 150s for this purpose. I do change my set up at least once per year and it is an added bonus that the refractor is much more robust to accommodate this.

I wrote that Astronomy Now article several years ago and have never been tempted to change my mind.  In fact the refractor was 5.5 inches, the TEC140.

What would tempt me, though, would be the RASA 11 or 14 with a small pixel CMOS camera. The depth of signal from fast optics means, in reality, being able to process harder.

Olly

Edited June 3, 2023 by ollypenrice
False click

[Rodd]

49 minutes ago, ollypenrice said:

I wrote that Astronomy Now article several years ago and have never been tempted to change my mind.  In fact the refractor was 5.5 inches, the TEC140.

What would tempt me, though, would be the RASA 11 or 14 with a small pixel CMOS camera. The depth of signal from fast optics means, in reality, being able to process harder.

Olly

Well, with respect to galaxies it’s ironic that I have a different experience.  The C11Edge beats the TOA 130 on galaxies hands down. Every time I have made a comparison, the C11 has won.  This is because those images were taken during decent seeing.  I have to disagree with you Olly on this one at your location. The crux of my post is that the TOA is the better scope FOR MY CONDITIONS. In Chile, the big aperture scope wins hands down for resolution, which galaxies are all about. A 5-6” scope just can’t pull out fine details as well as a big aperture scope when conditions allow the big scope to function as designed.  

[Rodd]

3 hours ago, tomato said:

I agree the TOA 130 is the better image. I was convinced by @ollypenrice’s article regarding using a 6” 1m FL refractor vs 2m+ FL reflector for galaxy imaging and do not regret going with Esprit 150s for this purpose. I do change my set up at least once per year and it is an added bonus that the refractor is much more robust to accommodate this.

In good seeing I would not agree.  If you take seeing (and other conditions) out of the equation, my post would be reversed. Aperture wins if conditions allow.  

[tomato]

I’m sure you are right but in the mostly damp and turbulent atmosphere above the UK, good seeing is even more rare than a clear moonless night.

[Rodd]

8 minutes ago, tomato said:

I’m sure you are right but in the mostly damp and turbulent atmosphere above the UK, good seeing is even more rare than a clear moonless night.

I guess the remote option is really the way to go.  If I knew then what I know now, I would have bought one scope and would have spent the rest of the budget setting up a remote observatory so I could image for real.

[ONIKKINEN]

12 hours ago, Rodd said:

This post id for those of you who insist the C11edge out perfroms the TOA 130.  Let's be clear--the C11Edge does outperfrom the TOA 130 in good seeing.

How is it possible that one scope takes bad data in poor seeing and one scope good data? Its not, if both datasets are treated equally at the same scale. You are comparing the C11 at its native scale to the TOA130 at its native scale, a comparison that has the goalposts moved so far that the argument in my opinion falls flat immediately. The "lost to wind" argument also doesn't make a whole lot of sense to me. Are you saying that binned x3 a large portion of the subs are still so far beyond salvation that they have to be scrapped entirely?

Again, if you bin/resample both the C11 and TOA130 images to the same size, the C11 will win every single time because it has more than 4x the aperture area. Clinging on to the argument that you dont want to bin is not the scopes fault, nor your skies' fault. If you really cant survive the horror of a non zoomable image because it is binned, then why not mosaic? You have 4x the aperture, you can afford to take extra panels for a target and still land in a "faster" image than the smaller scope. Just a simple 2 panel mosaic will create an image large enough to be zoomable on a 1080p monitor, and will still be much faster than the small refractor.

What is your plan here? So far not one of these sky complaint threads have had a conclusion.

[Rodd]

20 minutes ago, ONIKKINEN said:

How is it possible that one scope takes bad data in poor seeing and one scope good data? Its not, if both datasets are treated equally at the same scale. You are comparing the C11 at its native scale to the TOA130 at its native scale, a comparison that has the goalposts moved so far that the argument in my opinion falls flat immediately. The "lost to wind" argument also doesn't make a whole lot of sense to me. Are you saying that binned x3 a large portion of the subs are still so far beyond salvation that they have to be scrapped entirely?

Again, if you bin/resample both the C11 and TOA130 images to the same size, the C11 will win every single time because it has more than 4x the aperture area. Clinging on to the argument that you dont want to bin is not the scopes fault, nor your skies' fault. If you really cant survive the horror of a non zoomable image because it is binned, then why not mosaic? You have 4x the aperture, you can afford to take extra panels for a target and still land in a "faster" image than the smaller scope. Just a simple 2 panel mosaic will create an image large enough to be zoomable on a 1080p monitor, and will still be much faster than the small refractor.

What is your plan here? So far not one of these sky complaint threads have had a conclusion.

The conclusion here is obvious.  The TOA and C11 data are the same scale--same FOV.  and the TOA image is obviously better.  Regarding seeing, if the seeing is 2" and one scope shoots at .25" and one scope shoots at 1.5, the 1.5 will be better.  As far as binning--the reason I image with teh C11 Edge is to get close in shots.  If I have to bin 5x, what is the point?  the target galaxy would have the same screen size as a 5" refractor image without the FOV.  Pointless for my purposes.  I would rather use the 5" refractor and get a wider FOV around the galaxy of the same size.  It has nothing to do with zooming--it has to do with target size in the image.

The purpose here is to show that the TOA image zoomed is as good (in this case better) than the C11 image.  So the prupose is to show that I can image with the TOA and crop/upsample the im age so teh galaxy is teh same scale as the C11 image and be as good.  This image proves my point.  This is possible precisely because of the sky conditions.

Again, if you bin/resample both the C11 and TOA130 images to the same size, the C11 will win every single time--Not in this case!!!

[ONIKKINEN]

8 minutes ago, Rodd said:

The conclusion here is obvious.  The TOA and C11 data are the same scale--same FOV.  and the TOA image is obviously better.  Regarding seeing, if the seeing is 2" and one scope shoots at .25" and one scope shoots at 1.5, the 1.5 will be better.  As far as binning--the reason I image with teh C11 Edge is to get close in shots.  If I have to bin 5x, what is the point?  the target galaxy would have the same screen size as a 5" refractor image without the FOV.  Pointless for my purposes.  I would rather use the 5" refractor and get a wider FOV around the galaxy of the same size.  It has nothing to do with zooming--it has to do with target size in the image.

The purpose here is to show that the TOA image zoomed is as good (in this case better) than the C11 image.  So the prupose is to show that I can image with the TOA and crop/upsample the im age so teh galaxy is teh same scale as the C11 image and be as good.  This image proves my point.  This is possible precisely because of the sky conditions.

Again, if you bin/resample both the C11 and TOA130 images to the same size, the C11 will win every single time--Not in this case!!!

You conveniently ignored the entire point of my post. You can get the exact same wide field of view with the C11 with mosaics, and still be faster! There is no world in which a smaller scope gathers more photons than a larger one.

Best of luck with your imaging, i wont bother commenting on your threads anymore.

 

[Rodd]

4 minutes ago, ONIKKINEN said:

You conveniently ignored the entire point of my post. You can get the exact same wide field of view with the C11 with mosaics, and still be faster! There is no world in which a smaller scope gathers more photons than a larger one.

Best of luck with your imaging, i wont bother commenting on your threads anymore.

 

Mosaics--yeah.  It takes me weeks to do one panel--a mosaic takes months.  Not an option really. Not enough clear sky time.  I would need 6-8 panels.  That would not be faster

Edited June 3, 2023 by Rodd

[ollypenrice]

On 03/06/2023 at 13:05, Rodd said:

In good seeing I would not agree.  If you take seeing (and other conditions) out of the equation, my post would be reversed. Aperture wins if conditions allow.  

I agree with this, Rodd. I have excellent transparency but I don't think my seeing is generally exceptional. My findings with the refractor are specific to my own site.

Olly

Edited June 5, 2023 by ollypenrice
False click

[dan_adi]

On 03/06/2023 at 18:39, ONIKKINEN said:

You conveniently ignored the entire point of my post. You can get the exact same wide field of view with the C11 with mosaics, and still be faster! There is no world in which a smaller scope gathers more photons than a larger one.

Best of luck with your imaging, i wont bother commenting on your threads anymore.

 

In theory yes! But in practice ... have you worked with a SCT? They are by far the worse imaging platforms out there. I almost gave up on the hobby because I started imaging with a SCT.

Some points regarding my SCT: I could not efficiently prevent dew, I could not focus reliably with the stock focuser, the main mirror moved while slewing, mount modelling was worse , and I could go on ... but you get the point.

My solution to my SCT problem was a refractor. In my particular case a 8 inch CFF refractor. After I took a glance on a few  subs from the refractor compared to the SCT, I kid you not, I threw the SCT in the garbage bin.

Edited June 8, 2023 by dan_adi

[dan_adi]

On 03/06/2023 at 04:49, Rodd said:

This post id for those of you who insist the C11edge out perfroms the TOA 130.  Let's be clear--the C11Edge does outperfrom the TOA 130 in good seeing.  However, I rarely get good seeing.  Last night I lost 25% of my subs due to dewing issues with the C11Edge, and if breezy, I lose many more.  My point is on paper the C11Edge may outperform the TOA 130, but in the field, at my location, that represents maybe 10% of the time.  Maybe more--determining a number is impossible.  I'll just say it is less than 50% of the time.  And I think far less.

In this case I am comparing Ha stacks of the same target, registered to the C11Edge data.  The only processing that was perfromed was crop edges, DBE, and a histogram stretch to just below the noise threshold (or there abouts, there is still some noise as I wanted the images to be bright enough for this post).  the histpgram stretches were the same.  The TOA has a wider curve, which is apparent from the brightness, but the peaks of the histograms were in teh same location. The C11Edge image has 60 subs and the TOA image has 69 subs.  Most subs were 300 sec, but 12 subs for the C11EDge were 500 sec.  And still, the TOA image to my eye is better.  It has a lower FWHM (2.1 vs 2.4).  It is strange that teh C11 image is 9.4 mb while the TOA imnage is only 4.2.  Probably becuase the piel scale for the C11 image is .4" while the native piel scale of the TOA image was 1.12'.  I thought that when  registered, the pixel scales would become the same.  Apparently that is not the case.  In any event, if this is the difference between the two scopes most of the time, I resubmitt the query, why use the C11Edge?  The TOA can be cropped to the same size/scale.  The caveat is that I do not set up each night.  I switch scopes about once per year--sometimes every 2 years.  So using the C11 during good seeing and the TOA in less tha  goos seeing is not an option.

C11Edge

TOA 130

Had a simliar experience. In my case, Meade 12 inch SCT vs CFF 8 inch apo. Imagine your TOA being 8 inch! It will make the C11 look like a toy even on galaxies. Enjoy you TOA!

[Rodd]

5 hours ago, dan_adi said:

Had a simliar experience. In my case, Meade 12 inch SCT vs CFF 8 inch apo. Imagine your TOA being 8 inch! It will make the C11 look like a toy even on galaxies. Enjoy you TOA!

Well, here’s the thing.  In poor seeing, galaxies are out.  In good seeing the aperture wins.  In poor seeing, the only option is to image at a lower pixel scale. 

[Rodd]

5 hours ago, dan_adi said:

In theory yes! But in practice ... have you worked with a SCT? They are by far the worse imaging platforms out there. I almost gave up on the hobby because I started imaging with a SCT.

Some points regarding my SCT: I could not efficiently prevent dew, I could not focus reliably with the stock focuser, the main mirror moved while slewing, mount modelling was worse , and I could go on ... but you get the point.

My solution to my SCT problem was a refractor. In my particular case a 8 inch CFF refractor. After I took a glance on a few  subs from the refractor compared to the SCT, I kid you not, I threw the SCT in the garbage bin.

I can image with my edge just fine if the seeing is good.  

[licho52]

Based on threads like this and on CN I come to a conclusion that SCT really do a disservice to reflectors and tend to put people off working with reflecting telescopes.  I don't have any personal experience with SCT(I guess I am not losing much) but, based on the experience I do have, I know that a properly handled 10" Newtonian or Ritchey-Chretien would beat any 130mm refractor handily.

[Rodd]

1 hour ago, licho52 said:

Based on threads like this and on CN I come to a conclusion that SCT really do a disservice to reflectors and tend to put people off working with reflecting telescopes.  I don't have any personal experience with SCT(I guess I am not losing much) but, based on the experience I do have, I know that a properly handled 10" Newtonian or Ritchey-Chretien would beat any 130mm refractor handily.

This thread has nothing to do with telescope design. All we are talking about is aperture, focal length and pixel scale. 

[ollypenrice]

5 hours ago, licho52 said:

Based on threads like this and on CN I come to a conclusion that SCT really do a disservice to reflectors and tend to put people off working with reflecting telescopes.  I don't have any personal experience with SCT(I guess I am not losing much) but, based on the experience I do have, I know that a properly handled 10" Newtonian or Ritchey-Chretien would beat any 130mm refractor handily.

The problem with this assertion is that it rather glosses over so many variables. If you have the cash you can go out and buy an absolutely stunning refractor which needs nothing doing to it at all. In my case that's my TEC 140. It is plug and play. You cannot go out and buy a plug and play reflector, be it RC or Newt. The one that you do buy may have fatal flaws which need correcting before it can be used to a high standard. I agree with you that, once the multitude of sins contained in those two words 'Properly handled' are under control, the reflector should win. As for winning 'handily,' I'm not sure.

Can you link to an image from a 10 inch reflector which beats the TEC image handily? It can certainly be beaten, but 'handily?'

M51 TEC140 data only ( Olly Penrice ) - AstroBin

Olly

[vlaiv]

28 minutes ago, ollypenrice said:

Can you link to an image from a 10 inch reflector which beats the TEC image handily? It can certainly be beaten, but 'handily?'

What are parameters to judge the win?

Will integration time come into play? There is x4 difference in time between 10" and 5" which translates into x2 difference in SNR.

If we compare apples to apples - 10" might be marginally better in terms of resolution but it will certainly be quite a bit better in terms of SNR in a given time frame.

[ollypenrice]

31 minutes ago, vlaiv said:

What are parameters to judge the win?

Will integration time come into play? There is x4 difference in time between 10" and 5" which translates into x2 difference in SNR.

If we compare apples to apples - 10" might be marginally better in terms of resolution but it will certainly be quite a bit better in terms of SNR in a given time frame.

Indeed, more variables. I was thinking of final resolution, I guess. If I were to choose a galaxy imaging scope today it would be a RASA 14, in truth.

Olly

[vlaiv]

1 minute ago, ollypenrice said:

Indeed, more variables. I was thinking of final resolution, I guess. If I were to choose a galaxy imaging scope today it would be a RASA 14, in truth.

Olly

Regardless of its poor spot diagram?

That translates into ~1.64" at 790mm of focal length and that is RMS. Corresponding FWHM is x2.355 or ~3.86".

Further that means sampling at 2.4"/px, and this is limited by optics alone.

By the way, those 6.3um are not at the edges of the FOV - it is pretty much like that across the field:

[Rodd]

40 minutes ago, vlaiv said:

Regardless of its poor spot diagram?

That translates into ~1.64" at 790mm of focal length and that is RMS. Corresponding FWHM is x2.355 or ~3.86".

Further that means sampling at 2.4"/px, and this is limited by optics alone.

By the way, those 6.3um are not at the edges of the FOV - it is pretty much like that across the field:

I consider the RASA and hyperstar to be wide field systems. Imaging galaxies with a focal length less than 1,000 and a wide field is not ideal. The large spot size means that small pixels for a small pixel scale won’t work as well. This is a guess, but I have imaged galaxies at 700 mm and it’s nog ideal for any but the biggest 

[Rodd]

1 hour ago, ollypenrice said:

Indeed, more variables. I was thinking of final resolution, I guess. If I were to choose a galaxy imaging scope today it would be a RASA 14, in truth.

Olly

Another way to look at it is with a wider field instrument, most of the photons go into things other than the galaxy, where with a smaller field scope, most photons go into the galaxy.  If you crop the wider field image, you lose most of the photons.  

[ollypenrice]

7 hours ago, Rodd said:

Another way to look at it is with a wider field instrument, most of the photons go into things other than the galaxy, where with a smaller field scope, most photons go into the galaxy.  If you crop the wider field image, you lose most of the photons.  

I think this may be a misleading way to think about it. If we think in terms of 'object photons' (photons from the object) then the number captured depends only on aperture, provided the object fits on the chip. When you have a FL which lets the object cover the chip you are not exploiting more object photons than would be captured by a shorter FL of the same aperture. What you are doing is putting them onto more pixels for an improved spatial resolution at lower intensity of signal. The shorter FL doesn't waste any object photons - they are all used - provided you don't saturate the bright parts.  Only if you saturate the chip can you 'waste' photons because any more cannot be counted.

Olly

Edited June 9, 2023 by ollypenrice
Clarification